As an algorithm for adaptive array, a Minimum Square Error (MMSE) is known. The MMSE algorithm is a system for determining an optimal weight (MMSE weight) by minimizing the difference between a reference signal which is a desired array response and an actual array output signal (see Non Patent Literature 1).
Here, in communication standards such as WiMAX (Worldwide Interoperability for Microwave Access) and LTE (Long-Term Evolution), a plurality of users (terminals) can perform multiple access to a base station by a frequency division multiple access scheme.
A signal in the frequency division multiple access scheme (hereinafter, referred to as an “FDMA signal”) is composed of a plurality of subcarriers arranged side by side in a frequency direction. Therefore, to compute MMSE weights, signals (time domain received signals) received by a plurality of antennas, respectively, need to be subjected to a discrete Fourier transform (FFT; Fast Fourier Transform) to transform the signals into frequency domain received signals. The frequency domain received signals are used for computation of MMSE weights.
In addition, in the frequency division multiple access scheme, a minimum unit of resource allocation composed of a predetermined number of subcarriers and a predetermined number of symbols is set. For example, in LTE, the minimum unit of resource allocation to users is called a resource block. A resource block in LTE is formed as an area of 12 subcarriers×7 or 6 symbols and a communication frame is formed of a set of multiple resource blocks.
A base station performs resource allocation such that one or a plurality of resource blocks (minimum units of resource allocation to users) are allocated to each user terminal, and the base station and the user terminals perform communication using resource blocks according to the resource allocation.